Based on the rationale that useful pharmacological agents may be found, or leads developed from the study of animal toxins, we are engaged in the isolation and purification of toxic substances of animal origin. Primary among these products is the potent neurotoxin, atelopidtoxin, isolated from the skin of the Costa Rican frog, Atelopus chiriquiensis. This substance has an activity in the order of 5000 mouse units per milligram and causes death by cardiac failure. Apparently it is tetrodotoxin-like in its chemical structure but distinct both in its chemistry and pharmacology. We are engaged in the final purification and the proof of structure of atelopidtoxin. In addition exploratory studies are planned on toxic extracts of other animals, primarily of marine origin.